1. Field of the invention
The present invention relates to a surface acoustic wave device, and a manufacturing method therefor.
2. Description of the Related Art
A surface acoustic wave device has a surface acoustic wave element in which a interdigital transducer is formed on the surface of a piezoelectric element, and achieves electrical characteristics as an resonance circuit or a filter by the propagation of surface acoustic waves between the interdigital transducer.
Therefore, when a surface acoustic wave element is enclosed inside a surface acoustic wave device, space is required at least on the surface on which the interdigital transducer of the piezoelectric element is formed. Furthermore, since the propagation characteristics of a surface acoustic wave change when dust or moisture adheres to the interdigital transducer, it is desirable to hermetically seal the space on the surface where a interdigital transducer is formed.
One conventional method for satisfying such a requirement, for example, is a constitution in which the connection between the package and the piezoelectric element is connected by a bump, a stacked part serves as a wall, and, in addition, a lid is soldered on, as shown in Japanese Patent Laid-open No. H6-204293.
FIG. 1 is a diagram, which further illustrates a cross-sectional structure of such a conventional surface acoustic wave device.
The conventional surface acoustic wave device has a package substrate 1, which has a metallization pattern 10, and a piezoelectric element 3, which has a interdigital transducer 30 and pads 31, and the pads 31 of the piezoelectric element 3 are connected to the metallization pattern 10 of the package substrate 1 via bumps 2.
A hollow space for the interdigital transducer 30 is secured by the height of the bumps 2. Furthermore, electrical connections to the external connection terminals 11 of the package substrate 1 are formed by castellations 12.
Further, a package stacked part 4 is provided on the periphery of the package substrate 1 so as to surround the piezoelectric element 3, and a lid 5, which covers the piezoelectric element 3, is sealed by solder 13 to the upper part of the package stacked part 4.